This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. xc2xa7119 from my application INK SUPPLY VALVE OF A LIQUID ELECTROPHOTOGRAPHIC PRINTER filed with the Korean Industrial Property Office on Nov. 27, 1999 and there duly assigned Serial No. 53287/1999.
1. Technical Field
The present invention relates to an ink feeding system of a wet type electrophotographic printer and, more particularly, to an ink feeding valve having an improved structure for consistently feeding ink reserved in a concentrated ink tank to a developing solution tank.
2. Related Art
Generally, a wet type electrophotographic printer prints a desired image by forming an electrostatic latent image through the processes of: radiating a laser beam onto a photosensitive medium such as a photosensitive drum, a photosensitive belt, etc.; developing the electrostatic latent image with a developing solution of a certain color; and transferring the developed form to printed matter. Such electrophotographic color printers are mainly divided into wet type and dry type printers according to the kind of toner used. The wet type electrophotographic printer uses a developing solution which is composed of volatile liquid carrier and toner. The wet type electrophotographic printer has a higher print quality than the dry type electrophotographic printer which uses a power toner. Further, since the wet type electrophotographic printer does no harm in terms of toxic toner dust, the wet type electrophotographic printer is preferred to the dry type.
In the ink feeding valve described above, however, ink supply can vary due to different pressure of different ink amounts from the concentrated ink tank. Accordingly, the amount of ink supply can vary.
Further, in the ink feeding valve described above, there is or can be a problem of ink attachment to the inner side of the ink passage resulting in erroneous operation or, even worse, operational incapability. When such problems occur, the amount of ink supply becomes larger or smaller than required and, accordingly, the density of the developing solution is not maintained. Since such an inconsistent density of the developing solution has a negative effect on print quality, it is necessary to consistently feed concentrated ink. With the ink feeding valve described above, however, it is hard to adjust the density of the developing solution due to inconsistent concentrated ink supply.
The present invention has been developed to overcome the above-mentioned problems of the prior art and, accordingly, it is an object of the present invention to provide an ink feeding valve of a wet type electrophotographic printer capable of feeding consistent amounts of ink, regardless of pressure within a concentrated ink tank, by initially filling a certain volume of space with ink, before discharging ink to a developing solution tank.
It is another object of the present invention to provide an ink feeding valve of a wet type electrophotographic printer having a valve elevating section and an ink passage which are isolated from each other, and capable of operating efficiently without having ink attachment to the ink elevating section, and thereby capable of achieving consistent ink supply.
The above object is accomplished by an ink feeding valve of a wet type electrophotographic printer according to the present invention, including: a valve body having a pipeline interconnecting the concentrated ink tank with the developing solution tank; a rod assembly movable on the pipeline of the valve body within a certain vertical stroke for selectively opening/closing the pipeline; and an elevating section for vertically moving the rod assembly.
The valve body includes: an upper housing connected to a lower portion of the concentrated ink tank, and having a boss which has an ink inlet and which downwardly protrudes from the center of the upper housing; a bobbin having one end fixed to the upper housing, and the other end connected to the developing solution tank to define a pipeline; and an outer casing for covering the bobbin.
The rod assembly has first and second shutters disposed on upper and lower portions, respectively, of the rod to open upper and lower openings, respectively, of the pipeline alternately according to the vertical movement of the rod. When the upper opening of the pipeline is opened by the first shutter, the lower opening of the pipeline is closed by the second shutter. Accordingly, during the ink supply, ink flows from the concentrated ink tank to the pipeline in a certain volume sufficient to fill the pipeline, and then flows to the developing solution tank when the lower opening of the pipeline is opened by the de-elevating movement of the rod assembly. As a result, ink can be supplied in a consistent amount and in correspondence to the volume of the pipeline. In other words, ink can be consistently supplied from the concentrated ink tank, regardless of the amount of ink held in the concentrated ink tank.
The elevating section includes: an operation bar integrally connected to the center portion of the rod, a plunger disposed in the bobbin so as to be vertically moved along the inner circumferential surface of the bobbin, and having a stepped portion formed on the inner side for supporting both ends of the operation bar; a solenoid disposed between the outer casing and the bobbin for elevating the plunger by receiving electric current; a solenoid head formed on the upper inner side of the bobbin at a certain distance from the plunger for restricting movement of the plunger and a spring disposed between the upper housing and the operation bar for elastically biasing the operation bar downwardly.
Another object is accomplished by an ink feeding valve of a wet type electrophotographic printer according to the present invention, including a corrugated tube disposed on the pipeline of the valve body for partitioning the pipeline into an inside ink passage and an outside elevating section operating chamber on which the elevating section is mounted, thereby preventing flow of ink into the elevating section operating chamber.
Since the corrugated tube separately defines the ink passage and elevating section operating chamber, the elevating section is operated without having ink attachment thereto. Accordingly, the abnormality or undesirable operation due to ink attachment to the elevating section can be basically prevented.
An upper end of the corrugated tube is connected to an end of the boss of the upper housing, while a lower end thereof is fitted into a projection section inwardly protruding from the bobbin. Further, the corrugated tube includes two inwardly folded portions. These two inwardly folded portions are formed in symmetrical relation with each other by the operation bar located therebetween. When one folded portion contracts, the other extends. Further, it is preferable that the corrugated tube has such a diameter that an extreme inner end of the folded portion is spaced from the rod by at least 2 mm.
According to another preferred embodiment of the present invention, an ink feeding valve of a wet type electrophotographic printer includes: an upper housing connected to the lower portion of the concentrated ink tank, and having a boss downwardly projecting therefrom, the boss having an ink inlet formed on the center thereof for forming the ink passage; a bobbin having one end fixed to the upper housing and the other end connected to the developing solution tank for forming a pipeline; a rod having a first shutter and a second shutter disposed on the upper and lower portions, respectively, of the rod for closing upper and lower openings of the ink passage alternately, the rod vertically movable within the ink passage; an operation bar integrally connected with the center portion of the rod; a plunger vertically movable along the inner circumferential surface of the bobbin, and having a stepped portion for supporting both ends of the operation bar; a solenoid disposed outside the bobbin for upwardly driving the plunger by receiving electric current; a solenoid head disposed in the upper inner side of the bobbin at a certain distance from the plunger for limiting the movement of the plunger; a spring disposed between the upper housing and the operation bar for elastically biasing the operation bar downwardly; and a corrugated tube vertically extending between an end of a boss of the upper housing and the projection inwardly protruding from the lower side of the bobbin for preventing ink flow into the place where the plunger and spring are disposed.
According to still another preferred embodiment of the present invention, an ink feeding valve of a wet type electrophotographic printer includes: an upper housing connected to the lower portion of the concentrated ink tank, and having a boss downwardly projecting therefrom, the boss having an ink inlet formed on the center thereof for defining an ink passage; a bobbin having one end fixed to the upper housing, and the other end connected to the developing solution tank for forming a pipeline; a rod having a first shutter and a second shutter disposed on the upper and lower portions, respectively, of the ink passage for closing the upper and lower openings of the ink passage alternately, the rod being vertically movable within the ink passage; a plunger-operation bar integration connected to the center portion of the rod, and having a plunger portion integrally formed on both ends thereof; a solenoid disposed outside the bobbin for upwardly driving the plunger by receiving electric current; a spring disposed between the upper housing and the operation bar for elastically biasing the operation bar downwardly; and a corrugated tube vertically extending between an end of boss of the upper housing and a fixing member formed on the lower side of the bobbin for preventing ink flow into the space in which the plunger of the plunger-operation bar integration and the spring are disposed.